Food habits of the ferret (Mustela putorius furo L.) at Pukepuke Lagoon,New Zealand

The food habits of 44 tagged ferrets at a wildlife management reserve in the Manawatu dune country were examined from analysis of 333 scats, collected over a period of 34 months. Of the 203 scats containing prey, mammals occurred in 54.7%, birds and eggs in 33.5%, frogs in 17.2%, and eels in 13.3%. The 21 insects occurring in 10.3 % of the scats may have been taken as prey, but their importance in the diet is probably minimal. There was significant monthly variation in the occurrence of all prey groups, related to changes in availability or vulnerability of the prey populations. Female ferrets apparently ate the smaller prey items more often than males, but the differences were significant only for mice. No assessment of the effects ferrets have as predators on any of the prey populations is possible from this study.     

Conditional strategies and interpopulation variation in the behaviour of jumping spiders

Abstract

Conditional strategies and interpopulation variation in the mating and predatory behaviour of salticid spiders are reviewed. A functional approach is adopted, and defended, in which specified behavioural phenotypes are accounted for, in large part, by specified selection factors. Courtship versatility, in which a male's behaviour depends on the female's maturity and location, is common in the Salticidae. If a male encounters an adult female in the open, where there is ample ambient light, he performs vision-dependent displays (Type 1 courtship) in front of her. If he encounters an adult female inside her nest, he uses different displays (Type 2 courtship) which are not vision–dependent and consist of various tugging, probing and jerking movements on the silk of the nest. These displays apparently send vibratory stimuli to the female. When a male encounters a subadult female inside her nest, he initially performs Type 2 courtship, then spins a second chamber on the nest and cohabits until the female moults and matures. A modification of optimal foraging theory has been used to examine factors that influence interpopulation variation in male courtship persistence. A study of five populations corroborated predictions from the model. Persistence appears to be related to female availability. Female availability is related to local phenology, which is, in turn, related to local climate. Complex examples of predatory versatility also have evolved in the Salticidae, especially in the genus Portia. All species of Portia studied are araneophagic spiders that invade other spiders' webs and practise aggressive mimicry. Portia fimbriata, uniquely among Portia species studied, uses specialised behaviour to prey on other salticids. Portia fimbriata and one of the salticids on which it preys, Euryattus sp., appear to be co-adapted to each other.     

Spider predators of lepidopteran eggs in south Texas field crops

Observations were made of spiders attacking lepidopteran eggs in south Texas field crops (cotton, corn, and soybean) from 2001 to 2004. Twelve species of spider from seven families were observed feeding on the eggs during the 4 years. These spiders were primarily cursorial hunting spiders, and they were observed feeding on eggs most frequently in cotton, representing 26.6% of all observations in cotton over the 4 years. Spider predation on eggs was proportionally less frequent in corn and soybean with 6.3% and 15.4% of observed predation in those crops, respectively. Four species of spider were responsible for 86.1% of the predation by spiders. The anyphaenid Hibana futilis (Banks) was the spider most frequently observed feeding on lepidopteran eggs during the 4 years of this study, constituting 45.1% of all spiders observed. Grammonota texana Banks (Linyphiidae), Hibana arunda Platnick (Anyphaenidae), and Cheiracanthium inclusum (Hentz) (Miturgidae) were the 2nd, 3rd, and 4th most frequently observed spiders constituting 15.6%, 12.8%, and 11.7% of all spiders observed, respectively. Most spiders represented taxa that are known to forage without a web. However, G. texana was observed feeding on eggs independent of a web, which is uncharacteristic of linyphiids. Other cursorial hunting spiders feeding on eggs included members of the Clubionidae, Corrinnidae, and Salticidae. Ninety-eight percent of all observations of egg predation by spiders were nocturnal; only the Salticidae were diurnal. It is likely that previous studies of predation in crops have vastly underestimated the importance of spiders as predators of lepidopteran eggs due to inadequate evaluation of nocturnal predation.     

Jumping spiders attend to context during learned avoidance of aposematic prey

A large number of studies on both animals and humans have demonstratedthat learning is influenced by context or secondary cues thatare present when an association is formed. Few studies, however,have examined the functional value of attending to context.We first demonstrated that jumping spiders, Phidippus princeps,could be trained to avoid aposematic, distasteful milkweed bugs,Oncopeltus fasciatus. Spiders readily attacked bugs on firstexposure but were significantly less likely to do so after eighttrials, although they subsequently attacked and ate crickets.Spiders exposed to nontoxic milkweed bugs reared on sunflowerseeds did not show the same decline in attack rate. We nextexamined the effects of secondary contextual cues on spiderlearning by training spiders to avoid milkweed bugs in one oftwo environments. When spiders were tested in an environmentdifferent from the one in which they were trained, attack ratesincreased, and spiders no longer demonstrated retention of theassociation. Spiders tested in the same environment in whichthey were trained continued to avoid attacking the bugs. Theseresults have potential consequences for the evolution of bothpredator and prey and point to the importance of studying context-dependentlearning.     

Global diversity of true bugs (Heteroptera; Insecta) in freshwater

The aquatic and semi-aquatic Heteroptera, consisting of the infraorders Leptopodomorpha, Gerromorpha, and Nepomorpha, comprise a significant component of the world’s aquatic insect biota. Within these three infraorders as a whole there are currently 23 families, 343 genera and 4,810 species group taxa considered valid, of which 20 families, 326 genera and 4,656 species inhabit freshwater. In addition, more than 1,100 unequivocally diagnosed species remain to be described. Aquatic Heteroptera occur on all continents except Antarctica, and are most numerous in the tropical regions, although there are many distinctly cold-adapted genera. Overall species richness is highest in the Neotropical and Oriental regions, which harbor 1,289 and 1,103 species, respectively. In comparison to these core tropical regions, species richness is significantly lower in the Afrotropical (799 species), Australasian (654 species), Palearctic (496 species), Nearctic (424 species) and Pacific (37 species) regions. Aquatic Heteroptera are notable for utilizing an exceptionally broad range of habitats, from marine and intertidal to arctic and high alpine, across a global altitudinal range of 0–4,700 m. Species may be found in almost every freshwater biotope, and many exhibit striking morphological adaptations to their aquatic environment, making them excellent subjects for ecological and biogeographic studies. Guest editors: E. V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment     

Larval development of the cockle Chione stutchburyi (Bivalvia: Veneridae) reared in the laboratory

Abstract

Larvae of the New Zealand cockle Chione stutchburyi (Wood, 1828) reared to settlement in the laboratory are described. They are characterised by dissimilar shoulders with a large, broadly rounded anterior shoulder and end, and broadly rounded umbo, typical of the Veneridae. Setting occurred after 20 days at a minimum length of 180/µm. Shell dimensions increased linearly during larval development but hinge length did not. The L:H ratio decreased from 1.27 at L = 100 to 1.1 at L = 200 and the L:D ratio from 1.95 at L = 100 to 1.59 at L = 200. An SEM study revealed that the larval hinge is characterised by a toothed provinculum forming a broad medial projection on the right valve, opposing two projections on the left valve. Conspicuous flanges on the anterior and posterior shoulders of the left valve fit into corresponding grooves of the right valve.     

A novel property of spider silk: chemical defence against ants

Spider webs are made of silk, the properties of which ensure remarkable efficiency at capturing prey. However, remaining on, or near, the web exposes the resident spiders to many potential predators, such as ants. Surprisingly, ants are rarely reported foraging on the webs of orb-weaving spiders, despite the formidable capacity of ants to subdue prey and repel enemies, the diversity and abundance of orb-web spiders, and the nutritional value of the web and resident spider. We explain this paradox by reporting a novel property of the silk produced by the orb-web spider Nephila antipodiana (Walckenaer). These spiders deposit on the silk a pyrrolidine alkaloid (2-pyrrolidinone) that provides protection from ant invasion. Furthermore, the ontogenetic change in the production of 2-pyrrolidinone suggests that this compound represents an adaptive response to the threat of natural enemies, rather than a simple by-product of silk synthesis: while 2-pyrrolidinone occurs on the silk threads produced by adult and large juvenile spiders, it is absent on threads produced by small juvenile spiders, whose threads are sufficiently thin to be inaccessible to ants.     

Diet of intraguild predators affects antipredator behavior in intraguild prey

In two-predator, one-prey systems with intraguild predationand patchily distributed prey, the intraguild prey may facea choice between prey patches with and without intraguild predators.To minimize falling victim to intraguild predation, intraguildprey are expected to perceive cues specifically associated withthe presence of intraguild predators. We investigate whetherintraguild prey avoided intraguild predators and which cuestriggered this behavior in a system composed of plant-inhabitingarthropods. We found that intraguild prey recognized intraguildpredators from a distance, based on their diet: they avoidedodors of intraguild predators that had consumed shared preybut did not avoid odors of intraguild predators that had fedon other diets, including a diet of conspecifics. When intraguildprey were foraging on a patch, detection of intraguild predatorsled to longer periods of immobility and to fewer captures ofthe shared prey. However, intraguild predators that were eitherstarved or had previously consumed intraguild prey posed a higherrisk to intraguild prey than did intraguild predators that hadconsumed the shared prey. We conclude that the cues used byintraguild prey to avoid intraguild predators are associatedwith the circumstances under which they encounter intraguildpredators in the field and not to different degrees of danger.     

Experimental study of alarm calls of the oriental tit (Parus minor) toward different predators and reactions they induce in nestlings

Anti-predatory strategies of birds are diverse and may include predator-specific alarm calls. For example, oriental tit (Parus minor) parents can distinguish snakes from other predators and produce snake-specific referential vocalizations ("jar" call) when a snake poses a threat to their nest. The “jar” call has a very specific function to induce fledging of nestlings close to fledging age. This reaction ensures nestlings' survival in natural encounters with snakes that are capable of entering nest cavities and kill entire broods. Sciurid rodents, like chipmunks, may pose a similar threat to cavity-nesting birds. We explored the hypothesis that parents use the fledging-inducing alarm vocalizations in this situation, because chipmunks, like snakes, can kill the brood upon entering the nest cavity. We compared alarm calls of parents toward two predators (chipmunk and snake) who pose a similar threat to the nestlings in a nest cavity, and toward an avian predator (Eurasian jay) who cannot enter nest cavities and poses no threat to the nestlings in a nest. Our results show that the vocal responses of oriental tits were different among the three predators. This suggests that the acoustic properties of vocal responses to predators are different between predators of a similar hunting strategy (nest-cavity entering). The playback of recorded vocal responses of parents to chipmunks did not trigger the fledging of old nestlings, whereas the vocalizations toward a snake did, as shown by earlier studies. Our study suggests that the vocal response of parents does not carry information about the ability of predators to enter the nest cavity and confirms the special status of alarm calls triggered by snakes.     

Ontogenetic and temporal trajectories of chemical defence in a cyanogenic eucalypt

Many studies have shown that similarly aged plants within a species or population can vary markedly in the concentration of defence compounds they deploy to protect themselves from herbivores. Some studies have also shown that the concentration of these compounds can change with development, but no empirical research has mapped such an ontogenetic trajectory in detail. To do this, we grew cyanogenic Eucalyptus yarraensis seedlings from three half-sibling families under constant glasshouse conditions, and followed their foliar cyanogenic glycoside (prunasin) concentration over time for 338 days after sowing (DAS). Plants in all families followed a similar temporal pattern. Plants increased in foliar prunasin concentration from a very low level (10 μg cyanide (CN) equivalents g⁻¹) in their first leaves, to a maximum of, on average, 1.2 mg CN g⁻¹ at about 240 DAS. From 240 to 338 DAS, prunasin concentration gradually decreased to around 0.7 mg CN g⁻¹. Significant differences between families in maximum prunasin concentration were detected, but none were detected in the time at which this maximum occurred. In parallel with these changes in prunasin concentration, we detected an approximately linear increase in leaf mass per unit leaf area (LMA) with time, which reflected a change from juvenile to adult-like leaf anatomy. When ontogenetic trajectories of prunasin against LMA were constructed, we failed to detect a significant difference between families in the LMA at which maximum prunasin concentration occurred. This remarkable similarity in the temporal and ontogenetic trajectories between individuals, even from geographically remote families, is discussed in relation to a theoretical model for ontogenetic changes in plant defence. Our results show that ontogeny can constrain the expression of plant chemical defense and that chemical defense changes in a nonlinear fashion with ontogeny.     

Hyperparasitoid defense strategies against spiders: the role of chemical and morphological protection

The aphid endohyperparasitoid Alloxysta brevis(Thomson) (Hymenoptera: Charipidae) applies defensive chemicals stored in mandibular gland reservoirs against attacking ants. Alloxystines can be divided into species capable of exploiting ant-attended resources and into species exclusively reared from unattended aphid-parasitoid systems. Mandibular secretions are found in species of both groups, with little variation in chemical composition. We show that the mandibular gland secretion does not only protect against ant attacks but acts as an overall defense agent against generalist predators like spiders. The protective success differed with the spider species. The web-building spider Agelena labyrinthica(Clerck) (Araneae: Agelinidae) killed 57% of attacked A. brevisfemales, but sucked out only 8%. The smaller free-hunting jumping spider Salticus scenicus(Clerck) (Araneae: Salticidae) failed in overwhelming or severely injuring A. brevis. The pattern of interactions showed striking similarities with interactions between A. brevisand the ant Lasius niger(Hymenoptera: Formicidae). Primary parasitoids which are lacking chemical defense and sufficient morphological protection suffered significantly higher mortality due to spider predation. Our results indicate that – additional to chemical defense- parasitoid survival depends on the specific morphological resistance against grip pressure during capture, and on the predator – prey size relationship.     

Larval interactions in aphidophagous predators: effectiveness of wax cover as defence shield of Scymnus larvae against predation from syrphids

Small-sized predators in the aphidophagous guild of Aphis gossypii Glover colonies on hibiscus trees in Japan exploit aphids at low prey abundance. Scymnus (Pullus) posticalis Sicard beetles were the first predatory species to attack aphids in the spring, and their larvae co-occurred with larvae of Eupeodes freguens (Matsumura) syrphids in aphid-infested leaves of hibiscus for 3 weeks in absence of large-sized coccinellid predators. Larval interaction between Scymnus and syrphid predators was examined in relation to effectiveness of wax cover of Scymnus against predation from syrphids. Waxless first instar larvae were not protected but wax-covered larvae of second, third and fourth instars were protected from predation by syrphid larvae. The protection was lower in the second instar which has a thin wax cover and significantly higher in the third and fourth instars having a thick wax cover. In addition, larvae from which the wax was removed were significantly more vulnerable to predation. Vulnerability of Scymnus larvae to predation from syrphids was directly related to the thickness of wax cover. Results suggest that the wax cover of Scymnus larvae act as an effective defence mechanism against predation from syrphid larvae.     

Identifying the spatial scale of density-dependent interaction of predators with schooling fish in the southern Labrador Current

Previous work along the coast of Newfoundland has shown that aggregative responses of puffins, Fraiercula arctica , and common guillemots, Uria aalge , to schooling fish, primarily capelin, Mallotus villosus , occur at spatial scales of 2-6 km. The present work tests the hypothesis that coastal upwelling results in aggregation of capelin at this scale, and that the scale of interaction with predators can be predicted from wind-driven coastal upwelling. An observational experiment in 1987 showed that a relatively simple physical model could be used to predict the spatial scale of upwelling, that schooling fish aggregate at this scale after upwelling, that aggregation of schooling fish at the scale of upwelling decays as upwelling relaxes, and that the spatial association of puffins and guillemots with schooling fish reaches a maximum at this scale. These results suggest that relatively simple physical theory can, in some cases, be used to identify the spatial scale of interaction of predators with prey.     

Sticky predators: a comparative study of sticky glands in harpactorine assassin bugs (Insecta: Hemiptera: Reduviidae)

Zhang, G. and Weirauch, C. 2011. Sticky predators: a comparative study of sticky glands in harpactorine assassin bugs (Insecta: Hemiptera: Reduviidae). —Acta Zoologica (Stockholm) 00 : 1–10. For more than 50 years, specialized dermal glands that secrete sticky substances and specialized setae have been known from the legs of New World assassin bugs in the genus Zelus Fabricius (Reduviidae: Harpactorinae). The gland secretions and specialized ‘sundew setae’ are involved in enhancing predation success. We here refer to this predation strategy as ‘sticky trap predation’ and the specialized dermal glands as ‘sticky glands’. To determine how widespread sticky trap predation is among Reduviidae, we investigated taxonomic distribution of sticky glands and sundew setae using compound light microscopical and scanning electron microscopical techniques and sampling 67 species of Reduviidae that represent 50 genera of Harpactorini. We found sticky glands in 12 genera of Harpactorini and thus show that sticky trap predation is much more widespread than previously suspected. The sticky glands vary in shape, size and density, but are always located in a dorsolateral position on the fore tibia. Sundew setae are present in all taxa with sticky glands with the exception of Heza that instead possesses unique lamellate setae. The sticky trap predation taxa are restricted to the New World, suggesting a New World origin of this unique predation strategy.     

Convergence of chemical mimicry in a guild of aphid predators

Abstract.  1. A variety of insects prey on honeydew-producing Homoptera and many do so even in the presence of ants that tend, and endeavour to protect, these trophobionts from natural enemies. Few studies have explored the semiochemical mechanisms by which these predators circumvent attack by otherwise aggressive ants.
2. Ants use specific mixtures of cuticular hydrocarbons (CHCs) as recognition labels, but this simple mechanism is frequently circumvented by nest parasites that engage in 'chemical mimicry' of their host ants by producing or acquiring a critical suite of these CHCs.
3. Analysis of the CHCs from the North American woolly alder aphid, Prociphilus tessellatus (Homoptera: Aphididae), their tending ants, and aphid predators from three insect orders, Feniseca tarquinius (Lepidoptera: Lycaenidae), Chrysopa slossonae (Neuroptera: Chrysopidae), and Syrphus ribesii (Diptera: Syrphidae), showed that while the CHC profile of each predatory species was distinct, each was chemically more similar to the aphids than to either tending ant species. Further, the CHCs of each predator species were a subset of the compounds found in the aphids' profile.
4. These results implicate CHCs as a recognition cue used by ants to discriminate trophobionts from potential prey and a probable mechanism by which trophobiont predators circumvent detection by aphids and their tending ants.
5. Although several features of the aphids' CHC profile are shared among the chemically mimetic taxa, variation in the precision of mimicry among the members of this predatory guild demonstrates that a chemical mimic need not replicate every feature of its model.     

Variation in the effectiveness of abdominal shields of cassidine larvae against predators

The abdominal shields of the larvae of two tansy [Tanacetum (Chrysanthemum) vulgareL., Asteraceae] feeding species of Cassida (Coleoptera: Chrysomelidae) were tested for their ability to deter attacks by predatory insects. Cassida stigmatica Suffr. which carries an abdominal shield made of the exuviae only, and C. denticollis Suffr. which builds a compact faecal shield, were compared. Adult earwigs (Forficula auriculariaL., Dermaptera: Forficulidae), adult ladybird beetles (Coccinella septempunctata(L.), Coleoptera: Coccinellidae), and larval lacewings (Chrysoperla carnea Steph., Neuroptera: Chrysopidae) were used as predators and tested in dual choice bioassays. Against earwigs, shields of both cassidine species acted as a protective device. Earwigs preferred to feed on larvae without shields over larvae with intact shields. Adult ladybirds did not differentiate between C. stigmaticalarvae with and without exuvial shields. However, C. denticollis larvae with faecal shields were contacted at a higher frequency by ladybird beetles, even though they were less often consumed, i.e., their shield served as protection. In an olfactometer assay, faecal shields of C. denticollis were shown to have no attractive effect on the ladybird beetles. The protection for larvae with shields is likely to be caused by mechanical effects, namely the ability to move the shields. Control insects, where faecal shields of C. denticollis were glued on larvae of Galleria mellonella L. (Lepidoptera: Pyralidae), could not move their shields and were consequently consumed by the predator. Feeding by larvae of lacewings was not influenced by the presence or absence of the faecal shield. Thus, the effectiveness of the abdominal shields of tansy-feeding cassidine larvae varies with predator species, and might be based more on mechanical, than on chemical modes of action.     

人工巢箱繁殖鸟类主要巢捕食者及其影响因素

巢捕食是影响鸟类繁殖成功率的一个重要因素,也是鸟类繁殖生态研究中的一项重要内容。确定鸟类的主要巢捕食者及影响巢捕食的因素对于了解鸟类繁殖成功率、种群增长率及种群数量等具有重要意义。2009—2012年,对辽宁仙人洞国家级自然保护区人工巢箱中繁殖的杂色山雀(Parus varius)、沼泽山雀(P.palustris)、大山雀(P.major)和白眉姬鹟(Ficedula zanthopygia)四种鸟类的巢捕食率及影响巢捕食的因素进行了研究。研究共记录到238个繁殖巢(杂色山雀74巢、沼泽山雀21巢、大山雀118巢、白眉姬鹟25巢),其中35巢被捕食,捕食率为14.7%,雏鸟期被捕食占91.4%。巢捕食率在4种鸟类之间无差异(x~2=0.429,df=3,P=0.934)。以锦蛇(Elaphe spp.)为代表的蛇类是该地区小型森林洞巣鸟类繁殖期主要捕食者,占总捕食率的94.3%。对影响巢捕食的22个相关因子进行二元逻辑斯蒂回归分析发现,坡度、地面裸露率、草本盖度对巢捕食具有显著性影响;出雏时间、坡位、距碎石块距离对巢捕食的影响接近显著水平;而巢高、树粗、巢箱年龄、窝卵数、距路距离等对巢捕食无显著影响。因此,处于坡度较陡,坡位较高,草本覆盖率较高,地面裸露率较低,距碎石块距离较近,且出雏时间较晚的巢更容易被捕食。     

The evolution of colour polymorphism in British winter‐active Lepidoptera in response to search image use by avian predators

Phenotypic polymorphism in cryptic species is widespread. This may evolve in response to search image use by predators exerting negative frequency‐dependent selection on intraspecific colour morphs, ‘apostatic selection’. Evidence exists to indicate search image formation by predators and apostatic selection operating on wild prey populations, though not to demonstrate search image use directly resulting in apostatic selection. The present study attempted to address this deficiency, using British Lepidoptera active in winter as a model system. It has been proposed that the typically polymorphic wing colouration of these species represents an anti‐search image adaptation against birds. To test (a) for search image‐driven apostatic selection, dimorphic populations of artificial moth‐like models were established in woodland at varying relative morph frequencies and exposed to predation by natural populations of birds. In addition, to test (b) whether abundance and degree of polymorphism are correlated across British winter‐active moths, as predicted where search image use drives apostatic selection, a series of phylogenetic comparative analyses were conducted. There was a positive relationship between artificial morph frequency and probability of predation, consistent with birds utilizing search images and exerting apostatic selection. Abundance and degree of polymorphism were found to be positively correlated across British Lepidoptera active in winter, though not across all taxonomic groups analysed. This evidence is consistent with polymorphism in this group having evolved in response to search image‐driven apostatic selection and supports the viability of this mechanism as a means by which phenotypic and genetic variation may be maintained in natural populations.     

The effect of inbreeding on defence against multiple enemies in Datura stramonium

The ability of plants to respond to natural enemies might depend on the availability of genetic variation for the optimal phenotypic expression of defence. Selfing can affect the distribution of genetic variability of plant fitness, resistance and tolerance to herbivores and pathogens. The hypothesis of inbreeding depression influencing plant defence predicts that inbreeding would reduce resistance and tolerance to damage by natural enemies relative to outcrossing. In a field experiment entailing experimentally produced inbred and outcrossed progenies, we assessed the effects of one generation of selfing on Datura stramonium resistance and tolerance to three types of natural enemies, herbivores, weevils and a virus. We also examined the effect of damage on relative growth rate (RGR), flower, fruit, and seed production in inbred and outcrossed plants. Inbreeding significantly reduced plant defence to natural enemies with an increase of 4% in herbivore damage and 8% in viral infection. These results indicate inbreeding depression in total resistance. Herbivory increased 10% inbreeding depression in seed number, but viral damage caused inbred and outcrossed plants to have similar seed production. Inbreeding and outcrossing effects on fitness components were highly variable among families, implying that different types or numbers of recessive deleterious alleles segregate following inbreeding in D. stramonium. Although inbreeding did not equally alter all the interactions, our findings indicate that inbreeding reduced plant defence to herbivores and pathogens in D. stramonium.